28 STUDIES ON FEllMENTATION. 



heated glass and tlie hot liquid, and these will destroy the 

 vitality of any germs existing in such particles of dust as this 

 air may introduce. The re-entrance of the air will be effected 

 very gradually — sufficiently so to enable the drop of water 

 which the air, as it enters, forces up the curved tube, to 

 catch all particles of dust. Ultimately, the tube will become 

 dry, but then the passage of the air will proceed so slowly 

 that every foreign particle will get deposited on its interior 

 sides. 



Experience tends to prove that external particles of dust 

 cannot find their way into flasks of this pattern, having free 

 communication with the air, at all events within ten or twelve 

 years — the longest time that has been devoted to experiments of 

 this kind ; the liquid in the flasks, if originall)'' clear, will not 

 become in the least degree contaminated, either upon its 

 surface or throughout its bulk, although the outside of the flasks 

 may be covered with a thick coat of dust. This is an undeniable 

 proof of the impossibility of particles of dust finding their 

 way inside such flasks. 



Wort treated thus will preserve its purit}^ for an indefinite 

 time, notwithstanding its extreme liability to rapid change 

 when exposed to the air, under conditions which cause it to 

 come in contact with the particles of dust that air contains. 

 This also holds good in the case of wine, beef-tea, the must of 

 grapes, and, generally speaking, of all liquids which are subject 

 to putrefaction or fermentation, and which possess the faculty, 

 when their temperature is raised to about 100° C. (212° F.), 

 of destroying the vitality of those microscopic germs that are 

 found in dust. 



A flask such as we have described (Fig. 3) is all that we 

 require when we have to demonstrate the facts that we have 



Tantonville, in Tourtel's brewery, in carrjnng out certain practical ox- 

 perimonts in connection with the process that will be described in ote of 

 the later chapters of this work, wrote complaining that his flasks had 

 been suddenly invaded by a swarm of aphides, scarcely larger than 

 phylloxeras, and that manj' of them had even penetrated into the 

 inside of the curved tubes. 



